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Mitsubishi Electric MXZ-24UV -E2 Service Manual page 30

Inverter-controlled multi system
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• When cooling, heat exchanger of non-operating indoor unit frosts.
• When heating, non-operating indoor unit get warm.
(LED display: 0 0 0 0 , p p 1 1 )
D D Check of LEV
Start
Turn on power supply to the outdoor unit after checking LEV coil is mounted to the
LEV body securely.
Is "click - click" sound heard?
Or, do you feel vibration of the LEV coil with a hand?
No
Disconnect the connectors
(CN791: unit A, CN792: unit B, CN793: unit C).
Is there normal resistance to LEV coil?
No
Replace the LEV coil.
• When heating, room does not get warm.
• When cooling, room does not get cool.
(LED display: 0 0 0 0 , a a 8 8 )
E E Check of inverter/ compressor
Start
Disconnect the lead wire to the compressor at terminals, and turn on power supply to the indoor
and outdoor unit. Three minutes later, EMERGENCY OPERATION starts.
Measure the voltage between
each leading to the compressor.
U (BLK) - V (WHT)
V (WHT) - W (RED)
W (RED) - U (BLK)
Output voltage
COOL: 100V(58Hz) HEAT: 100V(58Hz)
Is voltage output? W1
Yes
No
Is output balanced?
Yes
Turn off power supply of indoor and outdoor unit,
and measure the compressor winding resistance
between the compressor terminals.
Is there resistance of 0.27" to 0.34" between
the each terminals?
Yes
Return the lead wire of compressor to former, and
turn on power supply to indoor and outdoor unit.
Three minutes later EMERGENCY OPERATION starts.
Clarify the causes by counting time until the inverter stops.
0 to 10 seconds: compressor rare short
10 to 60 seconds: compressor lock
60 seconds to 5minutes: refrigerant circuit defective
5 minutes or more: normal
Yes
Normal
Yes
Replace the electronic
control P. C. board.
W1 • After the outdoor fan starts running, wait for 1 minutes or more before
measuring the voltage.
• The output voltage values have the tolerance of i20%.
No
Is the overcurrent protection
shown on the LED monitor?
Yes
Replace the electronic
control P. C. board
with the I.P.M P. C. board.
No
Replace the
compressor.
Replace the
relay P. C. board.
30
1. Turn off power supply of the indoor
No
and outdoor unit, and disconnect
the connector CN 551 in the relay
P. C. board.
2. Turn on power supply to the outdoor
unit, and after 1 minutes or more
passed, check the resistance
between the connector
CN551 pin 1 and pin 2.
0"
Check the resistance
between each terminal.
Infinite
After 1 minute has passed since the
power supply of outdoor unit was
turned off, disconnect the connector
CN 553 in the relay P. C. board.
0"
Check the resistance
HPS (63H2).
Infinite
Replace the
HPS (63H2).

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